e2tools: new package

E2tools is a simple set of GPL'ed utilities to read, write, and
manipulate files in an ext2/ext3 filesystem.  These utilities access a
filesystem directly using the ext2fs library.

[Thomas: add toolchain dependencies as needed, use full Git hash, use
github helper, add support for host version.]

Signed-off-by: Daniel Nyström <daniel.nystrom@timeterminal.se>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>